CHAPTER 12: BEHAVIORAL FINANCE
AND TECHNICAL ANALYSIS
Technical analysis can generally be viewed as a search for trends or patterns in market prices. Technical analysts tend to view these trends as momentum, or gradual adjustments to ‘correct’ prices, or, alternatively, reversals of trends. A number of the behavioral biases discussed in the chapter might contribute to such trends and patterns. For example, a conservatism bias might contribute to a trend in prices as investors gradually take new information into account, resulting in gradual adjustment of prices towards their fundamental values. Another example derives from the concept of representativeness, which leads investors to inappropriately conclude, on the basis of a small sample of data, that a pattern has been established that will continue well into the future. When investors subsequently become aware of the fact that prices have overreacted, corrections reverse the initial erroneous trend.
Even if many investors exhibit behavioral biases, security prices might still be set efficiently if the actions of arbitrageurs move prices to their intrinsic values. Arbitrageurs who observe mispricing in the securities markets would buy underpriced securities (or possibly sell short overpriced securities) in order to profit from the anticipated subsequent changes as prices move to their intrinsic values. Consequently, securities prices would still exhibit the characteristics of an efficient market.
One of the major factors limiting the ability of rational investors to take advantage of any ‘pricing errors’ that result from the actions of behavioral investors is the fact that a mispricing can get worse over time. An example of this fundamental risk is the apparent ongoing overpricing of the NASDAQ index in the late 1990s. A related factor is the inherent costs and limits related to short selling, which restrict the extent to which arbitrage can force overpriced securities (or indexes) to move towards their fair values. Rational investors must also be aware of the risk that an apparent mispricing is, in fact, a consequence of model risk; that is, the perceived mispricing may not be real because the investor has used a faulty model to value the security.
There are two reasons why behavioral biases might not affect equilibrium asset prices: first, behavioral biases might contribute to the success of technical trading rules as prices gradually adjust towards their intrinsic values, and second, the actions of arbitrageurs might move security prices towards their intrinsic values. It might be important for investors to be aware of these biases because either of these scenarios might create the potential for excess profits even if behavioral biases do not affect equilibrium prices.
In addition, an investor should be aware of his personal behavioral biases, even if those biases do not affect equilibrium prices, to help avoid some of these information processing errors (e.g. overconfidence or representativeness).
Efficient market advocates believe that publicly available information (and, for advocates of strong-form efficiency, even insider information) is, at any point in time, reflected in securities prices, and that price adjustments to new information occur very quickly. Consequently, prices are at fair levels so that active management is very unlikely to improve performance above that of a broadly diversified index portfolio. In contrast, advocates of behavioral finance identify a number of investor errors in information processing and decision making that could result in mispricing of securities. However, the behavioral finance literature generally does not provide guidance as to how these investor errors can be exploited to generate excess profits. Therefore, in the absence of any profitable alternatives, even if securities markets are not efficient, the optimal strategy might still be a passive...
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